---
id: CVE-2026-0881
title: Sandbox escape in the Messaging System component
summary: >-
  Sandbox escape in the Messaging System component. This vulnerability was fixed
  in Firefox 147 and Thunderbird 147.
severity: critical
cvss: 10
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H'
cwe:
  - CWE-284
  - CWE-693
vendor: mozilla
product: firefox
affected:
  - firefox < 147.0
  - thunderbird < 147.0
patched:
  - firefox 147.0
  - thunderbird 147.0
published: '2026-01-13'
updated: '2026-06-30'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-0881'
references:
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=2005845'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-01/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-04/'
    label: security@mozilla.org
  - url: 'https://access.redhat.com/security/cve/CVE-2026-0881'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2428970'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-0881.json
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
tags:
  - nvd
epss: 0.00356
epssPercentile: 0.26616
ingestedAt: '2026-06-30T13:26:50.474Z'
---

## Overview

Sandbox escape in the Messaging System component. This vulnerability was fixed in Firefox 147 and Thunderbird 147.

## Affected

- `firefox < 147.0`
- `thunderbird < 147.0`

## Remediation

Upgrade past the affected range:

- `firefox 147.0`
- `thunderbird 147.0`